This invention pertains to improved components including a syringe and a check valve for a parenteral infuser, particularly but not exclusively an intravenous infuser. The infuser is preferably utilized for the administration of patient-controlled analgesia.
As manufactured by or for Abbott Laboratories, Hospital Products Division, North Chicago, Ill. 60064, and sold under its trademark "LifeCare", an intravenous infuser for patient-controlled analgesia ("PCA") comprises a pump, which is arranged to deliver individual, controlled doses of an infusible liquid containing an analgesic agent or agents, at patient-controlled intervals, for intravenous infusion into a patient. The patient is provided with a remote actuator or button, which he or she can press to actuate the pump. The pump is controlled so that it can be so actuated only if necessary conditions have been satisfied, e.g., only if a sufficient interval has passed since a prior dose was administered to the patient.
In the intravenous infuser described in the preceding paragraph, the pump, whenever so actuated, operates a syringe, which includes a vial and a plunger arranged within the vial for relative movement of the plunger and the vial along an axis of the vial. In use, the plunger is stationary, whereas the vial is movable. The syringe also includes a tubular needle, which extends through the plunger, and which conducts the infusible liquid to a check valve allowing the infusible liquid to flow, via a flexible tube, toward a site for intravenous administration to the patient. The check valve does not allow the infusible liquid, or any other liquid, to flow into the vial. The infusible liquid is caused to flow, as permitted by the check valve, upon relative movement of the plunger and the vial so as to shorten the chamber holding the infusible liquid. The infusible liquid is retained in the chamber, otherwise, by relative pressures on the infusible liquid.
Moreover, the syringe is provided with an annular flange, which fits into a cradle mounted on the pump. The pump is provided with a switch, which disables the intravenous infuser unless such a flange or an equivalent element is fitted into the cradle. The check valve is connected to the annular flange. However, since standard connectors, e.g., Luer connectors, are used not only to connect the check valve to the annular flange, as provided on the syringe, but also to connect the flexible tube to the check valve, it is possible for the check valve to be inadvertently or deliberately omitted and for the flexible tube to be directly connected to the annular flange. Without the check valve, if the vial of the syringe were to be accidentally cracked, siphoning could occur, which would be highly undesirable.